To learn how afferent discharges that originate from anterior tongue, posterior oropharynx and visceral organs interact in eliciting responses from central nervous system neurons during development, neurophysiological responses will be recorded in the nucleus of the solitary tract (NST) and parabrachial nuclei (PBN) in rats and four days postnatal through adulthood. When recording in the NST and PBN, taste receptors located on the anterior tongue and posterior oropharynx will be chemically stimulated with salts, hydrochloric acid, sucrose and quinine; the cervical vagus nerve, which transmits information from abdominal organs to the brain, will be electrically stimulated. As a correlate to these neurophysological experiments, a neuroanatomical study of the gustatory primary afferent nerve projections to the NST during development will be begun. The proposed studies will provide new information on: 1) how and when taste response characteristics change at each synaptic level throughout the rat's development when anterior tongue and posterior oropharynx are stimulated independently and simultaneously, 2) how and when vagal stimulation is received by chemosensitive neurons in the NST and PBN and the influence of vagal stimulation on taste responses, 3) how responses differ between the NST and PBN for each age, and 4) how the projections of gustatory and visceral nerves to the NST alter during development. The results will provide new information on the development of CNS taste responses, and correlative neuroanatomy, that relate to the development of taste preferences and aversions, and to the development of feeding and drinking.